When writing programmable completion functions, it would be very handy
to be able to instruct bash to ignore aliases inside functions. It's
often necessary to call things like sed, awk and grep inside completion
functions and, if the user has aliased these commands, all manner of
unexpected subtle errors can occur.

There's nothing preventing you from adding this protection. Aliases
are expanded when a shell function is read and parsed, not when it is
executed. One simply needs to bracket the programmable completion
function definitions with `shopt -u expand_aliases' and a corresponding
`shopt -s expand_aliases'.
Chet